Fortunately, JavaScript 1.2+ has incorporated regular expressions.JavaScript has an alternate syntax for creating Regular Expression objects that implicitly calls the RegExp constructor function.A regular expression pattern is composed of simple characters, such as /abc/, the syntax for that method is the following:

var RegularExpression = /pattern/[switch]

To use the Regular Expression object to validate the user input you must be able to define a pattern string that represents the search criteria. Patterns are defined using string literal characters and metacharacters. The following is some useful regular expression based javascript function, some works like validating user input will be very simple by using them.

This is complete crap.
Return the length of a string?
2 seperate email validators both of which fail?
Did you know that javascript already parses ints and floats.
Using these functions would actually be less secure

[...] number and decided to do a quick RegExp for validating a USA postal code with JavaScript(@see 10+ Useful JavaScript Regular Expression Functions to improve your web applications efficiency), in fact, Regular Expressions are included in most of the popular develop languages like PHP, [...]

… and by valid I mean services like Gmail strip out the dots in the username of an email address allowing users to accept email with any number of dots in the name. So, a.b.c @ gmail.com and ab.c @ gmail.com would both end up at abc @ gmail.com